Apparatus and Method for Quick Connect of a Plurality of Guns for Well Perforation

ABSTRACT

An apparatus and method for use for gun assembly for perforating wells comprising a plurality of guns with shape charges aligned centrically. The apparatus allows easier and more reliable assembly on site with more secure connections. The apparatus provides for the conducting of electrical signals and pressure through the end caps while preventing debris from the blast of one gun from entering and damaging the electrical connections and components of the next gun. The end caps being interconnected physically and electrically by specialized intermediate subs or by utilization with industry standard intermediate subs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) and P.C.T. Rule 4.10 from co-pending International Patent Application No. PCT/US2015/31047 filed in the U.S. Receiving Office, by Sergio F. Goyeneche, “Apparatus For Electromechanically Connecting A Plurality Of Guns For Well Perforation” filed 15 May 2015, which, by this statement, is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION Field of the Invention

This invention refers in general to an integral assembly (a “perf assembly”) of a plurality of perforating guns (“guns”) containing a plurality of shaped charges (“charges”). This perf assembly is used for perforation of wells to increase flow. This invention is particularly directed to a new coupling between a plurality of perf guns to allow faster and more reliable assembly and sequential firing of the guns during the perforation process of production wells.

This process of well perforation consists of the perforation of the metallic casing of a well, of isolating cement surrounding the casing, and of the layers of rock in the producing formation by means of explosives housed within perforating guns; achieving, through bore holes produced by a plurality of charges, a connection between the depths of the producing zone and the interior of the well. While this invention is generally found in the petroleum production industry, it may be equally applied to other environments where perforation of well casing into the surrounding environment is necessary, such as water wells.

Background of the Invention

The perforation of producing wells is realized by lowering into the well a perf assembly comprised of a plurality of guns each containing a plurality of charges. The guns are connected by intermediate subs containing pass through openings for wiring. A firing wire, coupled with the casing as a ground, carries an electrical signal through the well bore to connect with each gun and allow firing of the detonators. The detonators may be fired through independently addressable switches or through a series of pressure switches and diodes which isolate each gun until the desired firing event. The perf assembly is then retrieved from the well hole and the subs are disassembled and saved for reuse. Undetonated explosives are safely disposed of, and the remaining assembly, consisting of pierced pipes, wires, and electronics are then disposed.

One method of independently firing the guns is to use individually addressable detonators such as those described in U.S. Pat. Nos. 8,091,477 and 8,230,788. Another method of independently firing the guns is to connect each gun through a pressure sensitive switch which grounds the detonator of each gun until the pressure of the previous gun's firing triggers the switch to an active state. Further, diodes are used to cause each gun to require a polarity reversal from the signal which fired the previous gun. This prevents the signal from propagating throughout the assembly as the blasts set each pressure switch sequentially, and the pressure switches prevent the later guns from firing before the previous ones.

This method requires a continuous electrical signal to run the length of the perf assembly. However, wires are often twisted, broken, or can pull loose during the assembly process during the act of screwing the subs together. This results in the assembly having to be deconstructed and repaired. Additionally, weakened wires may pass initial test during construction only to fail during the process of lowering the assembly to depth, or due to vibrations of early charges in the sequence. Additionally, the manual assembly process, when rushed, may be prone to wiring mistakes and other human error.

The preferred method is to fire the farthest/lowest gun first. Then, sequentially fire each gun back toward the well opening. This is because the explosion/pressure/debris from one gun's firing can possibly damage adjacent guns. Wires can break or connectors can loosen during shockwave vibrations, or by blast force. With pressure switches, any damage requires retrieval of the perf assembly for correction, as the rest of the assembly is now non-fireable.

Addressable switches allow a damaged section to be skipped, but still result in unfired guns, which must be retrieved from the hole. Unfired guns are highly undesirable, as they are hazardous to bring to the surface due to the dangers of handling explosives which are not known to be in a safe condition or state.

To fulfill the operation so briefly described above, while simultaneously respecting existing norms for the manipulation of explosives, highly capable operators are required to arm and assemble the guns and the wellhead, stripping the ends of connecting wires and joining them by twisting the exposed portions of the wire together and covering the joint with adhesive electrical tape, resulting in an ‘artisanal’ activity requiring extreme caution. While this assembly process should be carefully completed and verified multiple times, it is just human nature to rush and possibly shortcut while performing this operation in the rain, cold weather, or other adverse conditions that are undesirable to the operator.

It should be noted that petroleum production and exploration activities are generally located in areas with hostile climatic conditions for the operators; work hours are assigned in accordance to the needs of the operation and may include nighttime and daytime hours, with extreme cold or heat, rain or wind, darkness or sunlight.

Hours are controlled by working against the clock and by penalizing setbacks; to that respect, it is absolutely necessary that the strictest safety norms be followed while handling explosive material; all of these factors together contribute to an increased likelihood that operators may commit errors while wiring or assembling the guns into a perf assembly to be introduced into the well. Further, even if the operators do everything correctly, the actions required to connect the pipe sections that make up the perf assembly may still produce a costly mistake.

Once the fracturing operations are complete, the perf gun must be disassembled. The operators must separate the pierced gun casings from the sub connectors joining the guns, remove any wiring and or electronics. Once the equipment has been disassembled and separated, the sub connectors between the guns, which are costly and reusable, are set aside for later operations. The wiring and electronics are disposed of along with the pierced gun casing and the remaining parts of the perf assembly.

From the above facts, there exists an obvious need to simplify the operation of arming and joining the guns into a perf assembly. There is also a need to ensure that the firing of one gun does not introduce faults into the remaining portions of the perf assembly preventing the required firing sequence. The object of this invention deals with the means to reduce the time and effort required on site to perform the gun assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of an assembly of multiple armed and assembled guns in a manner that is utilized in the industry.

FIG. 2 shows a cross section of a single gun joined on each end with a tandem sub assembly.

FIG. 2A shows an insulator cap assembly prior to mating with the gun or sub.

FIG. 2B shows a bottom sub assembly containing a detonator attached to a bottom sub and mated with a perf gun.

FIG. 3 shows two guns joined by a sub assembly where in the pressure/diode switch is mounted in the sub assembly and placed in contact with the retractable contact pin installed into an insulating top end assembly of one of the guns.

FIG. 4 shows two guns with insulating contact pins in each end joined by a sub assembly incorporating a feed through pin to connect there between.

FIGS. 5A, 5B, and 5C are views of a pressure switch end cap for securing a pressure/diode switch in accordance with an exemplary embodiment of the innovation.

FIG. 5D is a perspective view of a pressure/diode switch and end cap in accordance with an exemplary embodiment of the innovation.

FIGS. 6 and 7 illustrate the assembly of two perf guns joined by a short sub.

FIG. 8 is cross section of a perf gun assembly, explosives omitted for clarity, illustrating the use of end caps, insulated contact pins, and an short sub.

FIG. 9 is cross section of a plurality of assembled perf guns and a quick change pin box for connection to the firing controls.

FIG. 9A is an enlarged cross section view of a perf gun connected to a quick change pin box.

DETAILED DESCRIPTION OF THE INVENTION

In the previous application, which is referenced and incorporated above, the inventor discussed, inter alia, utilization of improved gun performance via specialized end caps on the guns to protect the wires of other guns in the perf assembly during handling and blasting operations. However, the previous application still utilized intermediate sub-assemblies (referred to as tandem subs) for joining together the plurality of guns which resulted in the tandem subs needing to be retrieved from between the guns after firing. It also requires extending wires through tandem subs which may twist as the sub-assemblies are assembled.

More reliable assembly can be accomplished if there is a safe way to prepare and wire perf gun segments in a controlled environment in such a manner that the segment can be safely transported to a well site and joined with other segments to produce the needed perf gun apparatus for use in the well. A plurality of independent shape charged shots are sequentially positioned and wired to a pressure/diode switch, secured centrally in an end cap at one end, and wired to an insulated polarized-charge carrier contact pin at the distal end to produce a shot assembly.

The shot assembly is secured internally in a gun body casing via snap rings fitted to a groove at the internal end of standardized pipe threads internal to and located at the ends of the casing to produce a perforating gun segment. The pressure/diode switch is recessed in the gun body casing, which may be temporarily enclosed with an insulating protector cap to allow safe transportation and storage of the perforating gun assemblies. The distal end's contact pin projects from the end of the gun body casing and may also be temporarily enclosed with an insulating protector cap secured to the internal threads of the body casing allowing safe transportation and storage of the perforating gun assemblies.

Once assembly is commenced at the site a plurality of the perforating guns are joined there between by short intermediate subs which allow the insulated polarized-charge carrier contact pin of one gun assembly to be positioned in contact with the pressure/diode switch of the neighboring gun assembly, completing the electrical circuit from one end of the perf gun to the distal in with a continuous electrical and physical contact.

In another embodiment, a plurality of guns with intermediate/tandem sub-assemblies and pressure/diode switches may be pre-assembled before transportation to reduce site prep work. Sub-assemblies maybe manufactured from low-grade steel, plastics, fiberglass, or other material of sufficient strength to support the weight of the gun assembly and securely connect it to the drill pipe. One skilled in the art would understand that use of a non-conductive material such as plastics or fiberglass would also require an integrated conductor to ensure proper electrical grounding between the various assemblies.

Currently in the industry a plastic insulating or a metal bottom end cap attaches to the charge carrier, and approximately centers it within the gun body. The bottom end cap has a central hole through which passes a wire carrying the electrical firing signal. A second wire connects to a grounding pin affixed to the plastic end cap or to the metal end cap which is routed to contact against the gun body to establish a ground. Any of these wires may be broken or disconnected during assembly and therefore prior assembly and testing in is preferred.

In the preferred embodiment, the perf gun has a recessed insulated contact pin held by a connector end cap in a central orientation at one end. The distal end has a recessed pressure/diode switch held by a connector end cap in a central orientation. A tandem sub with a feed thorough pin can connect the insulated contact pin of the connector end of one perf gun to the pressure/diode switch of the distal end of the neighboring gun to ensure physical and electrical contact throughout the entire perf gun assembly.

In another embodiment, only one of the two neighboring guns is configured in accordance with the innovation described herein. That perf gun has a recessed insulated contact pin held by a connector end cap in a central orientation at one end. In such a situation, a tandem sub with a pressure/diode switch is joined to the gun and the wires from the pressure/diode switch are connected to the neighboring gun in a traditional manner of the current practices in the industry.

In another embodiment, that perf gun has a recessed pressure/diode switch held by a connector end cap in a central orientation. In such a situation, a tandem sub with a feed through pin is joined to the gun and distal end of the feed through pin is connected to the firing wire of the neighboring neighboring gun in a traditional manner of the current practices in the industry.

The innovation includes replacing the traditional plastic or metal end caps on each charge carrier with an improved design which is more robust and reliable in the assembly of multiple guns into a single perf assembly as taught in the prior application, and includes an additional design for a robust and reliable end cap which houses a pressure/diode switch.

In the new innovation, the end cap of one perf gun positions the insulated contact pin to extend just past the end of the gun casing. The end cap of the neighboring perf gun positions the pressure/diode switch slightly recessed within the end of the gun casing. A disposable short sub assembly joins the two neighboring perf guns by threading into the ends of each and thus placing the insulating contact pin of the first perf gun in contact with the pressure/diode switch of the second perf gun.

The improved design eliminates the through hole in the center of the bottom end cap, which was previously used to pass wires through for connection, and allows the connection to be made by simply screwing the two guns together with the disposable short sub assembly. This eliminates the difficulty of ensuring proper wiring and operation. Further, the disposable short sub assembly does not need to be retrieved from between the guns after firing, or more importantly in instances of misfires which leads to handling explosives in an unknown state.

DETAILED DESCRIPTION OF THE DRAWINGS

The following is a detailed description of exemplary embodiments to illustrate the principles of the invention. The embodiments are provided to illustrate aspects of the innovation, but the invention is not limited to any embodiment. As those skilled in the art will appreciate, the scope of the invention encompasses numerous alternatives, modifications, and equivalent; it is limited only by the appended claims.

FIG. 1 is a cross-section of an assembly of multiple armed and assembled guns in a manner that is utilized in the industry. The perf assembly (1) has a firing head (2), a plurality of perforating guns (3), each containing a charge carrier, two tandem subs (4), and a bottom sub (5).

FIG. 2 shows a cross section of a single gun joined on each end with a tandem sub assembly. The gun (3) comprises a charge carrier (13) with a plurality of explosive shape charges (16) joined by a detonation cord or fuse (19). The charge carrier (13) is supported, substantially centered, within the gun body casing (12) by an insulating top end (14) and an isolating bottom end (15).

One can see in the interior of the carrier (13) that the shaped charges (16) are shown set in radial fashion, that is to say, perpendicular to the gun wall, to the carrier, and, when the guns are within the well, to the well casing. In the illustration, six shape charges are illustrated, but the actual number and orientation will vary.

The shaped charges are explosives set in such a manner that they concentrate the force of the explosion outward, generating a jet of gas (plasma) at high pressure and temperature, that pulls the metal from the interior of the charge and projects it outward until it arrives at the well formation; with this action the charges produce a perforating effect that is variable in proportion to the potency of the charges.

In each intermediate joint or intermediate sub or tandem sub (4) one can see the pressure activated changeover switch (17), from which wires extend to the rest of the assembly. When the detonator is activated, a detonation is propagated by way of a “fuse”—or detonating cord (19)—to each of the shaped charges in the carrier (13) that burst in simultaneous fashion within the corresponding gun (3). Although not described in detail herein, the internal details of the assembly are protected by a watertight seal; otherwise the liquids present in the well would enter into the interior of the gun causing problems with the electric and/or ballistic systems.

In FIG. 2A, the insulating end plate is represented as being attached to the lower end of the charge carrier (13), and has a tab for connecting the ground wire (22) from the carrier to the interior of the gun housing; furthermore, it has a hole, or central orifice, (23) that permits the passage of a pair of wires, ‘live’ or ‘fire’ (F) and ‘ground’ (G). These wires are connected to the components in the next tandem immediately below to pass the signal throughout the assembly (1, not illustrated) as required by the electronic configuration thereof.

In FIG. 2B, the insulating end plate (15) centers the charge carrier (13) and causes the grounding contact (22) to connect with the gun body (12) represented as being attached to the lower end of the charge carrier (13), and has a tab for connecting the ground wire (22) from the carrier to the interior of the gun housing; furthermore, it has a hole, or central orifice, (23) that permits the passage of a pair of wires, ‘live’ or ‘fire’ (F) and ‘ground’ (G). These wires are connected to the components in the next tandem immediately below to pass the signal throughout the assembly (1, not illustrated) as required by the electronic configuration thereof.

FIG. 3 shows two guns joined by a sub assembly where in the pressure/diode switch is mounted in the sub assembly and placed in contact with the retractable contact pin installed into an insulating top end assembly of one of the guns. The gun body casing (12) encloses the charge carrier (13) which contains the plurality of explosive shape charges (16).

A firing signal wire (F) carries the firing signal through the insulated contact pin (500), which is secured in the connector end cap (400) by a nut (550) to secure it and allow movement by the spring (540) which urges it outward to contact the pressure/diode switch (17) secured by a snap ring (600) in the tandem sub (4). The wires (F and G) carry the firing signal from the pressure/diode switch (17) to the neighboring gun. The neighboring gun in this illustrated exemplary assembly does not have an incorporated pressure/diode switch.

FIG. 4 shows two guns with insulating contact pins in each end joined by a sub assembly incorporating a feed through pin to connect there between. In this illustrated exemplary assembly each gun (12) comprises a snap ring (600) securing a connector end cap (400) having a central insulated contact pin (500) which passes the firing signal to the addressable switch (620) in each gun. The guns are joined by an intermediate sub (4) which has a central feed through pin (610) electrically and mechanically linking the insulating contact pins (500) of each gun (12).

FIGS. 5A, 5B, and 5C are views of a pressure switch end cap for securing a pressure/diode switch in accordance with an exemplary embodiment of the innovation. The pressure switch end cap (700) is manufactured from a durable solid material which is electrically conductive. In the preferred embodiment the end cap is manufactured from aluminum. The pressure switch end cap (700) has an inner face (710) and an opposing outer face (720).

The outer face (720) has a recessed O-Ring (730) for sealing against the short sub (not illustrated), when one is used for assembly of guns. The inner face (710) has an edge, the charge carrier mating surface (740) which mates with the charge carrier of the gun, and is secured thereto with pins through the screw holes (745). A guide pin (760) extending from one edge of the pressure switch end cap (700) prevents the cap from turning once it is mated to a guiding groove in the gun body casing (12, not illustrated).

The inner edge of the guide pin (760) is beveled (765) to assist in insertion into the gun body casing (12). Guide points (770) aid in centering the cap in the gun body casing while minimizing contact to reduce insertion force required seating the cap. The inner face of the cap includes an opening (780) for the electrical wires of the pressure switch to pass into the gun body casing (12).

FIG. 5D is a perspective view of a pressure/diode switch and end cap in accordance with an exemplary embodiment of the innovation. The pressure/diode switch (17) has an electrically conductive pressure activator (20). The body of the pressure/diode switch has one or more O-rings (630) which securely fit the central opening of the pressure switch end cap's (700) outer face (720).

The pressure switch end cap (700) has another O-ring (730) around the outside of the outer face (720) to contact with the short sub. The guide pin (760) and guide points (770) ensure a centrally located and non-twistable connection with the gun body casing (12).

FIGS. 6 and 7 illustrate the assembly of two perf guns joined by a short sub. In the referenced drawings, the left side is the upper gun, and the right side is the lower gun. The gun body casings (12) include threads to mate with the pipe threads (940) of the short sub (900).

The pressure switch end cap (700) and the connector end cap (400) seat into voids in the short sub (900) so that the pressure/diode switch (17) is in electrical contact (20) with the insulating contact pin (500) of the neighboring gun. O-rings (630) ensure a water tight seal and prevent contaminants from entering the guns at the short sub.

FIG. 8 is cross section of a perf gun assembly, explosives omitted for clarity, illustrating the use of end caps, insulated contact pins, and an short sub. The charge carrier (13) with its plurality of shape charge openings (16A) is secured co-axially with the gun body casing (12). One end has a pressure switch end cap (700) into which a pressure/diode switch (17, not illustrated) may be placed during final assembly.

The distal end of the charge carrier (13) has a connector end cap (400) containing an insulating contact pin (500) inserted into the lower side opening (920) of the short sub (900). The short sub (900) with O-rings (630) is threaded (940) to the end of the gun body casing (12) securing the charge carrier (13) therein. A plurality of recesses for O-rings (950) on the upper side of the short sub (900) ensure water tight seals when the neighboring gun is threaded (940) on to secure the pressure/diode switch (17) in the upper side opening (930).

FIG. 9 is cross section of a plurality of assembled perf guns and a quick change pin box for connection to the firing controls. FIG. 9A is an enlarged cross section view of a perf gun connected to a quick change pin box. Continuing from FIG. 8, the upper side opening (930) of the short sub (900) is mated to the right side of FIG. 9 with the pressure/diode switch (17) being placed in contact with the insulated connector pin (500) of the lower side gun.

At the top of the gun, illustrated on the left side of FIG. 9, a terminating sub (670) connects to the short sub (900) to secure a quick change pin box assembly (800) to the gun. An extending pin (810) and extension spring (820) are secured with a retainer clip (840) to allow the Quick connector pin (830) to protrude from the top of the entire gun assembly for connection of the firing signal wires.

The diagrams in accordance with exemplary embodiments of the present invention are provided as examples and should not be construed to limit other embodiments within the scope of the invention. For instance, heights, widths, and thicknesses may not be to scale and should not be construed to limit the invention to the particular proportions illustrated. Additionally, some elements illustrated in the singularity may actually be implemented in a plurality. Some element illustrated in the plurality could actually vary in count. Some elements illustrated in one form could actually vary in detail. Such specific information is not provided to limit the invention.

The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications. 

What is claimed is:
 1. A gun assembly for perforating wells comprising; a plurality of gun body casing, the casing being a hollow cylinder, with a threaded coupling at each end; a charge carrier, the carrier being a hollow cylinder, with exterior diameter less than the interior diameter of the casing, and a length shorter than the gun body casing; a plurality of shape charges positioned radially inside the charge carrier and inter connected by a detonator cord; a plurality of end caps affixed to the ends of the shape charges and axially aligning the carrier within the casing; the end caps securing electrical connectors which pass electrical signals to the charge carrier detonation electronics; at least one intermediate coupling with thread boxes on each end for joining the threaded coupling of two axially aligned gun body casings such that the end caps are placed in contact within the intermediate coupling.
 2. The assembly of claim 1 wherein the intermediate coupling is made of a plastic material.
 3. The assembly of claim 2 wherein the intermediate coupling further comprises an electrical conductor spanning between the thread boxes to electrically connect the pipes assembled thereby.
 4. The assembly of claim 1 wherein the intermediate coupling is of a lower grade disposable metal material.
 5. The assembly of claim 1 wherein the intermediate coupling is attached to a gun body end to secure the electrical connector to the end cap of the charge carrier.
 6. The assembly of claim 1 wherein at least one electrical connector is an insulated contact pin.
 7. The assembly of claim 1 wherein at least one electrical connector is a pressure/diode switch.
 8. The assembly of claim 1 wherein the intermediate coupling is attached to a gun body end to cover and protect an end cap during shipping of the assembly.
 9. The assembly of claim 1 wherein the intermediate coupling further comprises a feed through pin electrically and mechanically connecting the charges end caps of two axially aligned gun body casings.
 10. A method of assembling a perforation gun assembly comprising: assembling a plurality of shape charges radially aligned and facing outward from the axis of a charge carrier body; connecting the shape charges by a detonation cord; connecting the detonation cord to an electrical signal carrier; connecting the electrical signal carrier to an insulated contact pin; securing the insulated contact pin in an end plate at the end of the charge carrier: extending the electrical signal carrier to the distal end of the charge carrier; securing the charge carrier in a gun casing body; optionally installing protective covers over the ends of the gun casing body.
 11. The method of claim 10 further comprising connecting the electrical signal carrier at the distal end of the charge carrier to an insulated contact pin.
 12. The method of claim 10 further comprising connecting the electrical signal carrier at the distal end of the charge carrier to a detonator and pressure/diode switch.
 13. The method of claim 10 further comprising connecting the electrical signal carrier at the distal end of the charge carrier to a detonator and addressable switch.
 14. The assembly of claim 10 wherein the insulated contact pin is connected to a quick connector pin.
 15. The assembly of claim 10 wherein the insulated contact pin is connected to a quick change pin box assembly comprising: an optional extending pin box; an extension spring; and a quick connector pin, electrically insulated from the gun casing body, and electrically connected to the insulated contact pin and secured extending axially from the end of the gun casing body. 